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PREFACE TO THE SECOND EDITION. 



The favourable reception and rapid sale of the first edition 

 of the Conchological Manual having rendered a second neces- 

 sary, the Author takes this opportunity of explaining the 

 nature of the alterations which have been made. In doing 

 this, he has to thank his friends for their suggestions, which, 

 together with his own increased knowledge and experience, 

 enable him to present a more complete and satisfactory work 

 to the scientific public. 



For the further convenience of those who are studying the 

 rudiments of the science, an entirely new Introduction is 

 given, in which, commencing with the structure and gradual 

 developement of the shell, the author has endeavoured to 

 explain the general principles of Conchology in systematical 

 order. This Introduction is illustrated by 100 wood-cuts, 

 which will be found greatly to assist the Student. 



The definitions have been rendered more full and complete 

 than before, and the Author has profited by some manuscript 

 notes communicated by a scientific friend, to whom he desires 

 to present his humble acknowledgments. Upwards of four 

 hundred explanations have been given of words which did not 

 appear in the former edition, three-fourths of which are of 

 generic and subgeneric names. 



A large number of notes, referring to the geographical 

 distribution of the genera, have been added from the pen of 

 Mr. G. B. Sowerby, Senior, 



